Method of bending metal strips



Jan. 30, 1945. w. SCHUKRAFT 2,368,163

7 METHOD OF BENDING METAL STRIPS Filed Dec. 14, 1942 2 Sheets-Sheet l WZZZg znz Sdzukraf Gavan ---YMMJ Jan. 30, 1945. w. SCHUKRAFT METHOD OF BENDING METAL STRIPS Filed Dec. 14, 1942 2 Sheets-Sheet 2 Patented Jan. 30, 1945 -UNITED :STATES {PATENT OFFICE :METHO'D-OFBENDING METAL- STRIPS William, Schukraft,.Chicago, Ill.

Application'December 14, 1942, Serial No." 468,922

.9 Claims,

'iThe invention relates to a method of bending -metalstrips and more particularly to the-bending of long, straight-thin and relativelyiwide strips into a form; in which they are arcuate longitudinally substantially in the; plan thereof.

The present invention has particular utility'in the fashioningof metal' strips used in airplane constructions. Referring particularly to the deicer arrangements as used'on certain airplane r constructions, the sheet' of rubber which is disposed-over the leading edges'of the..wings and are formed by an extruding process. However, the de-icer assemblies require ,in :addition to straight'strips, some-that: are arcu-ate longitudinally substantially-in their planes, to "follow. the

radius on-whichthe wingtips and "edge surfaces the thinner edge is the inner edge.

The; general aim-of the invention. is to provide a novel method for forming such longitudinally arcuate stripsrapidly and efliciehtly,

Another object istqprovide a newandir'nproved method ofithis character. in which one; or "more "straight-strips to be bent. are ,confined tightly against any .movementtransversely of their planes, as -by1being encased in a heavy metal enclosure, the entire ..unit then being bent to impart thejdesired curvature to the encased strips and transverse bending .or buckling being substantially prevented by the. heavy enclosure means.

Inconjunction with theforegoing, an object is 'to-provide in sucha method the steps of bending the encased unitsfirstwtoia-smaller radius than that "desired and ithen reversing the bending to the desired radius whereby to further diminish the buckling effect.

' Another object is to -providea novelme'thod of Other objects and advantages WiII "become apparent in the following descriptionand from the accompanyingdrawingssinwhichz Figure 1 is-aperspectiveviewof'a straight metalstrip prior'to'bending'by the process embodying the features of't he invention.

Fig. 2 isaside viewpf an'encased unit-after bending.

Fig. 3 is a; perspectiveviewof-a bent-strip after =-removal from .the encasing means and showing '10 the buckling effect -on -an"ei aggerated scale. I

Fig. 4 is anendvieworanencased unit before "bending.

"Fig. 5- is aview similar to Fig. 4 ona slightly 'reduced scale showing-a slightly modified *arrangement-of the strips inthe enca'sing means.

Fig. 6 shows partially in end elevation and partially-in cross; section"a modified {form or en- "casing'means.

Fig; 7'showsthe "modified form of Fig. 6 in' side elevation and illustrates both the initia1 and *bent form of "the encased'um't.

'-'Fig.' 8. is a' View similar to Fig." 6==showing= another :modified form of encasing means.

While "the invention is susceptible of various 5 modifications "and alternative constructions, I

have'shown in' the drawings and will hereindescribe in detail the preferred embodiment, but it is-to be understoodthatiI-do'not thereby intend to limit" the invention to the specific form or procedure"disclosed,'but' intend to cover -'-a;l1'-- mo"difi "cations and alternative methods falling 'within thespiritand-scope of the invention asexpressed in theappende'd'claims. I

As previously mentioned, the present-invention finds J particular applicationin- 'the formation of ;'the elongated strips'of thepeouliar forrn required in" the installation of de-icer assemblies. Accordingly," the invention will be' considered in this environment but it' will "-be evident that the "novel--method has widerapplicationthan this specific instance.

.Referring to ".the drawings, Fig. 1 illustrates s ight elongatedst'rip*oraluminum' or aluminum: alloysuch as :is "used to Efix'the marginal :ofthe leading. edges of the'wing or tail assemirblies. This stripdesignated lll'is usually formed by an extruding process and inone' formis about *tWOHiIIChSSTWldB- Its length is asrequiredand its thickness 'varies" from a relatively thick edge ll about 1 5'" or s s"-"thick-to-a'thin featheredge l2. It is slightly'arouatein transverse'cross sectioni'sothat itsputersurface' in assembly will complement the surface of the structure to which "it is'secure'd.

The invention in this particular embodiment is employed to bend such strips into a form arcuate longitudinally substantially in the plane of the strip, the direction of bending being such that the feather edge 12 has the shorter radius.

Obviously bending thin metal strips in this fashion, whether the strips be flat or of arcuate cross section, is extremely difficult because the metal, particularly along the edge of shorter radius, will buckle or become transversely distorted so that the resulting strip would have an edge surface of generally serpentine form. This difficulty, of course, would increase to a considerable extent in the bending of a tapering sheet in which the inner edge is extremely thin.

According to the present invention, such strips may be conveniently bent to desired form with a minimum of rippling or buckling effect. Thus, a plurality of strips, having the straight form showing in Fig. 1, are stacked together in faceto-face abutment as shown at l3 in Fig. 4, and in this condition they are tightly confined so that they have approximately a unitary relation. To so confine the strips, encasing means is provided which in the present instance includes a pair of side plates 14 and a pair of end plates ii. The side plates l4 are complemental in form to the outside surfaces of the stack of strips, whereby these plates have substantially full surface engagement with the'outer strips. The plates may be dimensioned so that all four sides of the stack are engaged and confined, but tight confinement of the edges on the outer or greater radius (the thicker edges as shown) is neither essential nor as desirable. The primary factor is tight, compressive lateral confinement throughout the areas where buckling ordinarily would occur.

The plates I4 and I5 are heavy sturdy members of steel or the like having sufficient strength substantially to prevent movement or displacement of metal laterally or transversely of the direction in which the unit is bent. The plates are rigidly secured together in any suitable manner, as by being welded together, as at l6. The welding is preferably done while the stacked strips and the encasing plates are under at least lateral compression.

The unitary assembly thus formed is then bent to the desired radius, the direction of bending in this particular form of strip being toward the feather edges thereof. This may be done in any well known manner as by rolling the unit in a roller or pressing it into the desired radius in a hydraulic press or a press brake.

When the encased unit has been formed to the desired radius the encasing plates I4 and I5 are removed and the stacked strips separated. In spite of the confining pressure on the strips while they are bent, it may be that small ripples, as indicated at l1 in Fig. 3, will have formed in the edge portion of the strip. These ripples, however, are relatively small, the extent of rippling being held to a minimum by the confining effect of the encasing means. I have found that the size of the ripples can be further reduced by first bending the encasing strips to a smaller radius than that desired in the completed form followed by a reverse bending to the desired radius. In other words, the strips are first bent too far as indicated by the dotted outline l8 (Fig. 3) followed by a reverse bending to the required radius as indicated by the full outline.

The ripples H are exaggerated and may be quite readily removed from the bent strip by any suitable operation. For example, the technique all) used in reconditioning automobile fenders may be employed involving the hammering down of the high spots and filing or otherwise smoothing the strip into finished condition.

Strips for de-icer assemblies are used in pairs on the opposite margins. These pairs are substantially alike except that the transverse arcuate faces are reversed. The present invention may be used to form such pairs simultaneously. Thus, as shown in Fig. 5, two stacks of strips are simultaneously encased in opposed relation as with the transverse arcuate faces of one stack opposing the arcuate faces of the other stack. The stacks could as well face in the opposite direction. The two stacks are separated by a central partition l9 having opposite faces 20 complemental to the inner faces of each of the stacks. This partition accordingly is thin at the thick edges of the strips and thick at the feather edges. This partition together with the side plates H are arranged to complement and fully'abut the exposed concave and convex surfaces of the strips. The unitary structure thus formed is bent and the resulting strips are subsequently smoothed in the manner previously described. By this process opposed pairs of longitudinally bent strips may be conveniently and accurately formed.

In Figs. 6 and '7 a modified form of encasing means is shown which may be repeatedly used. The illustrated arrangement is one in which strips in pairs are bent as in the form shown in Fig. 5, but it will be understood that a single set, stack or group of strips can be bent as well. Referring to Figs. 6 and 7, one surface of a base plate 2| of substantially heavy metal stock has a thin plate 22 integrally united along each longitudinal edge thereof as by welding, indicated at 23 (Fig. '7)

The side or lateral support comparable to that afforded by the side plates l4 of the encasing structure shown in Figs. 1 to 5 is provided by sets of thin fiat plates 24 arranged to be stacked in flat face abutment on the plates 22. The outer edges 25 of the sets are fashioned to be in substantially perpendicular alinement to the base plate 2| while the inner edges 26 are shaped to complement the contours of the outer surfaces of a stack of strips to be bent. The assembled sets of plates 24 therefore have full surface engagement with the outer strips and provide the required lateral confinement. The plates 22, rigid with the base plate, provide inwardly facing shoulders which define fixed and laterally unyielding positions for the strips. A flat cover or top plate 21 completes the encasing structure. Where, as shown, the strips are to be bent in opposed pairs, a center set of plates 28 is provided having edge surfaces 29 complemental to the surface portions of the strips to be engaged thereby.

Between their ends the base plate 2 l the plates 22, the cover plate 21, and the plates 24 are preferably secured rigidly together on each side of the structure by a sturdy plate 30 welded or otherwise suitably secured to each of the individual parts. At the ends of the unit the parts may be less permanently but tightly connected as by U shaped members or clips 3! each arranged to straddle the top and sides of the unit with their ends extended through openings 34 in a base plate abutting cross bar 32. Nuts 33 on the extended ends secure the parts tightly together. Preferably the encasing unit is somewhat longer than the strips to be bent,

as indicated at 34, to insure that the end portions of the strips will be bent to th same radius as the central portions.

Thearrahgerhentshowrvimli'igs: S and 7-is who preferred over the otlier fomwbecause great latera-1 'resistancea is provided "by -the: series. of thin, substantially unconnected plates -yet theiunit has relatively highfieiiibih'tydn the directioninwhich bending =is'- to take-plaice The confiningplates may be fashioned== of 'mild or'- cold rolled 'steel" or made of spring steel-'sdthataiter abending opera tion they may be easily reshaped to theiroriginal flatwormfor reu-sea During bndin g the plates of the assembly-may shift relatively to some extent avoi'dingmnnecessary stresses and "distortion of the-parts? The modified iorm of-iencasing means shown in Fig. *8 is in efict': substantially acombination of the forms of FlgszA-orfi and Ei g. 6. l Thus, -refer'- ring-- to Fig tithe encasing meansdncludes anend plate-351%(obmparable -.to th'e end :plate I- at e the thinner edges: of the stripsi side plates 36 (c'om'- parable toz 'the -sid'e plates-1:1) and in'the illustratedform'a-central partition 3! (comparable to th partition I9). The side plates and the end plate are welded together as in the form of Figs. 4 and 5. However, the opposite end plate at the thicker edges of the strips is a channel member 38 so dimensioned that its legs 39 fit snugly against the outer faces of the side plates 36'. Centrally located lugs or reenforcing plates 40 (comparable to the lugs or plates 30 of the form of Figs. 6 and 7) are preferably secured, as by welding, to the legs 39 of the channel member and the end plate 35. At each end the parts of the encasing unit Fig. 8 may be secured together by the same clip means described in connection with the unit of Figs. 6 and 7. Since these parts are unchanged they are indicated by the same reference numerals.

The encasing unit of Fig. 8 is advantageous in that it may be quickly and easily assembled and disassembled. Moreover it affords the necessary transverse rigidity opposing the tendency of the thinner edges of the strips to buckle while being somewhat less confining to the thicker edges. This factor is important in that it permits the thicker edges some movement other than lateral during the bending operation.

It will be evident from the foregoing that a novel method of bending an elongated thin and relatively wide strip edgewise into a form which is arcuate longitudinally substantially in the plane thereof has been provided. The process is simple and may be rapidly carried out. While a single strip may be bent according to the process if desired, eflicient production practices make the simultaneous bending of a plurality of strips more desirable. It will, of course. be understood that the present invention has utility in the bending of :trips that are not of tapering arcuate cross secion.

I claim as my invention:

1. The method of bending thin elongated metal strips in the plane thereof while avoiding substantial buckling along the strip which includes the steps of tightly confining a plurality of such strips in stacked face-to-face abutment and supporting the entire face of each strip within a bendable encasing means which is rigid in a direction transversely of the stacked strips, bending the encasing means with the stacked strips therein in a direction which bends the strips edgewise. thereby bending the strips to a smaller radius than the radius desired, reversely bending said encasing means and strips to the desired radius, removing the encasing means, and smoothing such irregularities as may have resulted during bending.

2;: Thermethod of bendingthin.elongatedmetal strip's of arcuate'cross sectionzin .the. plane; there'- ofi while avoidinglsubstantiat buckling-along: the strip which includes the stepsofitightlyi confining aplura'lity of such strips inwstacked: faceeto-face abutmenti and :;supporting the. entire; outer: side faces oi each strip- 'within a bendable :encasing means which isv rigid .in 1 a direction; transversely ofthe'sta'cked strips having full .iacecontact with the outer side facesofnthe stacked-strips;;bending theencasing: means with the stacked strips therein in a direction which bends the;strips:-edgewise, and-thereby. bending thestrips'toi a .smallerradius than the zradiustdesired reversely: bending. said encasingimeansi and strips. to. the. desirednradius. removing the: encasing means,t and finishing. the strips/ 3.11 The method-or :hending; thin :elonga-tedmetal strips; having a; cross sectional. form. which; is

arcuate and .tapersrin thickness,v the direction of bending beingrsubstantia lly in the. plane. thereof which includ'esxthe: StEDSiOfZ confining :undercom: pression a plurality of such strips in face-to-face abutment and supporting the entire face of each strip within a bendable encasing means which is rigid in a direction transversely of the stacked strips, bending the encasing means with the stacked strips therein in a direction which bends the strips edgewise, and thereby bending the strips to a smaller radius than the radius desired, and reversely bending said encasing means and strips to the desired radius.

4. The method of bending edgewise thin elongated rnetal strips of arcuate cross section which includes the steps of arranging a. plurality of such strips in stacked face-to-face abutment, confining and supporting the entire faces of a pair of such stacks within a rigid encasing means which is rigid in a direction transversely of the strips, with the arcuate faces of the stacks disposed oppositely, bending the encasing means with the stacked strips therein in a direction which bends the strips edgewise, and thereby bending the strips to a smallerradius than the radius desired, and reversely bending said encasing means and strips to the desired radius.

5. The method of bending edgewise thin elongated metal strips which have a cross sectional form arcuate and of tapering thickness which includes the steps of confining such strips in opposed relation within a rigid but bendable encasing means, maintaining bysaid confining means full surface abutment with at least one of the edges and with the exposed convex and concave surfaces of said strips, bending the encasing means with the strips therein in a direction which'bends the strips edgewise, thereby bending the strips to a smaller radius than the radius desired, and reversely bending said encasing means and strips to the desired radius.

6. The method of forming thin and wide metal strips of arcuate cross section into pairs of complementary strips having a form arcuate lengthwise substantially in the plane thereof which in cludes applying a bending force to a pair of oppositely facing strips to bend them edgewise while confining the edges and side faces of the strips on the inner radius tightly against buckling, and thereby bending the strips to a radius greater than desired, and while the strips remain so confined reversely bending them to a desired radius.

7. The method of bending thin and wide metal strips to curve such strips lengthwise substantially in the planes thereof without substantial buckling of the side edges toward which such taneous bending of the reenforcing members and strips are bent, which comprises, compacting a bundle of such strips in face-to-face stacked relation with reenforcing members overlying the opposite faces of the stack and contacting such faces throughout the entire areas of the same which are to be bent, and applying bending forces to said reenforcing members to bend the same and the confined bundle of strips edgewise while retaining the bundle tightly confined by the reenforcing members in the course of the simul- 8. The method of bending thin and wide metal -.strips to curve such strips lengthwise substantially in the planes thereof without substantial lbuckling of the side edges toward which such strips are bent, which comprises, stacking a bundle of such strips in faoe-to-face relation, compacting the bundle by pressing a pair of metal reenforcing plates against the opposite faces of the stack, which plates are of heavy stock as compared to the strips and dimensioned to contafct the faces of the stack throughout their entire area for the length of the same which is to be bent, permanently seaming a pair of top and bottom plates to the edges of the first-mentioned reenforcing plates, bending the stack of strips and encasing plates in a direction edgewise of the stack, and breaking the seams and removing the reenforcing plates only after the bending is completed.

9. The method of bending edgewise thin am I V 

